Heavy bullets for the ar 15

[Wil@SniperCompany]

Check with the manufacturer prior to loading up a lot of bullets. The 77 gr. Sierra BTHP bullets I have tried have a warning on the box. The warning says to use only in 1-8 or tighter twist barrels. A heavier bullet has to rotate faster to stabilize. Light bullet in a 1-7 or 1-8 twist barrels have been known to explode from over rotation while going down range prior to hitting a target. Do your own homework and make your own decisions. I have found over the years that some mis-information gets posted on this sight.

While your information is true, I have found to be velocity dependent. If I can push the 77s just fast enough (nothing stupid), you can get them to stabilize very well in a 1:9. For the lighter varmint bullets... I too, have seen them spin apart from over rotation. I believe this too is velocity dependent. If you slow them down a bit they will fly well in a faster twisted barrel.... Let's not forget that barrel length can play into this as well.

 

[Wil@SniperCompany]

It's not the weight of the bullet that factors into twist rate, it's the length. But yeah, heavier bullets are usually longer.

And I've heard of bullets ripping themselves to shreds from too fast of twist rate all the time, but I don't think I've seen anyone come up with real evidence of it happening.

You bring up an excellent point with the mention of bullet length... It's not so much the length that is the concern, but the bearing surface that will actually contact the rifling, etc.

 

[Texas42]

There aren't that many, non-lead bullets, which means most bullet's weight correlates with the length, give or take. Barnes TSX and others are all copper. Copper is lighter than lead (and therefore the bullets are long for weight).

I sold my 1/9 twsit upper, and never fired anything other than 55 grain. My 1/7 twist does shoot the 70 grains barns TSX well, though
EDIT: here is a 52 SMK, a 55 grain FMJ-BT, and a 70 grain TSX HP-BT.

 

[Wil@SniperCompany]

I've also found this true... I shoot the 62gr TSX in my 1:9 twist, but I've noticed that I can transpose some of the 77SMK load data for this bullet, as their bearing surfaces and OAL are very similar. When shot side by side, they performed similarly out to 500 for me as well...very similar dope (within .2 mils).

 

[Txhillbilly]

Hornady makes a 75gr BTHP match bullet for 1-9 twist.
I shoot them a lot out of my Savage 12,and have shot them out of a 16" AR with 1-9 twist.

 

[randmplumbingllc]

It is not so much about the weight, as it is the length of the bullet.

It is called the "Greenhill Formula"

Greenhill Formula

The link above does all the work for you......that is if you are reloading. If buying loaded ammunition, you will have to see if you can find the bullet specs., or pull a bullet and measure.